The long-term objectives of this doctoral research are to improve the understanding of diarrheal disease in children in developing countries. More specifically, this research will: 1. Examine the adverse effect of diarrheal disease on child growth. 2. Determine whether the effect of diarrhea on growth is the same for all causes or whether some diarrhea pathogens are more responsible for growth faltering than others. 3. Determine whether growth deficits resulting from diarrhea recover with time (i.e., whether children catch- up in growth after diarrhea). 4. Identify epidemiologic factors that determine the rate of catch-up growth. The understanding of the effect of diarrheal disease on growth is of critical importance in the design and conduct of diarrheal control programs. If it is true that a small group of pathogens cause most of the growth retardation in the community, then 1) control program should target these specific pathogens through prompt identification treatment or through vaccination programs and 2) diarrheal disease research funding should be directed towards feeding supplementation research, micronutrient research, or vaccine development for specific pathogens that currently do not have available vaccines. The mechanisms by which diarrhea causes growth retardation are poorly understood. Epidemiological studies can offer important clues in understanding the pathophysiology of diarrhea-related growth retardation which in turn could improve treatments leading to growth recovery.